fix(coverage): c8 provider to work when isolate:false

packages/coverage-c8/src/takeCoverage.ts

@@ -5,10 +5,12 @@
 import inspector from 'node:inspector'
 import type { Profiler } from 'node:inspector'
 
+// Create a single session when coverage provider is loaded inside worker or child_process
 const session = new inspector.Session()
+session.connect()
 
+// Note that this may be called multiple times in a single worker/process, depending on "isolate" configuration
 export function startCoverage() {
-  session.connect()
   session.post('Profiler.enable')
   session.post('Profiler.startPreciseCoverage', {
     callCount: true,

test/coverage-test/testing.mjs

@@ -23,15 +23,19 @@ const configs = [
   }],
 ]
 
-for (const threads of [true, false]) {
-  for (const [directory, config] of configs) {
-    await startVitest('test', [directory], {
-      ...config,
-      update: UPDATE_SNAPSHOTS,
-      threads,
-    })
+for (const threads of [{ threads: true }, { threads: false }, { singleThread: true }]) {
+  for (const isolate of [true, false]) {
+    for (const [directory, config] of configs) {
+      await startVitest('test', [directory], {
+        name: `With settings: ${JSON.stringify({ ...threads, isolate, directory })}`,
+        ...config,
+        update: UPDATE_SNAPSHOTS,
+        ...threads,
+        isolate,
+      })
 
-    if (process.exitCode)
-      process.exit()
+      if (process.exitCode)
+        process.exit()
+    }
   }
 }